Circuit breaker



oct. 2z, 1957 R. STEINER 2,810,802

CIRCUIT BREAKER Filed Novf 5, 1954 j 47 9o rl' 38 'I' Ill 5e rn 88 l F as 4o l III' 82 92 lr l l 91 y s4 l y i I M w 14 4`2 94 4 14 I l M d l .Il 'I' f/ 13 INVENTOR. RUDOLF sTE|NER QUT- m AT TORNE YS nited States Patent CIRCUIT BREAKER Rudolf Steiner, Levittown, Pa., assignor to the United States of America as represented by the Secretary of the Navy Application November 5, 1954, Serial No. 467,248

8 Claims. (Cl. 200-87) (Granted under Titia 35, U. S. Code (1952), sec. 265) The invention described herein may be manufactured and used by or for the Government of the United States of America for governmental purposes without the payment of any royalities thereon or therefor.

The present invention relates to a circuit breaker and more particularly to a circuit breaker having an electromagnetic overload sensing means directly effective in response to an overload condition to produce separation of the electrical contacts within the circuit breaker.

There are various known types of circuit breakers which are operated on the electromagnetic principle which share a common advantage over the various types of circuit breakers that operate on the thermal principle. First, the electromagnetic type circuit breakers are inherently fast actingy while thermal type circuit breakers are characteristically relatively slow acting. Second, the operation of electromagnetic type circuit breakers is not aected by the ambient temperature as is the operation of thermal type circuit breakers. Third, electromagnetic type circuit breakers may readily be made available to operate at any desired rating while thermal type circuit breakers can only be provided to operate at relatively widely spaced rating increments. Notwithstanding their inherent advantages the electromagnetic type circuit breakers presently available are limited in their utility by certain disadvantages. Regardless of their detail design features these mechanism are generally relatively complex and consist of many individual parts. For example, it is common to find that a circuit breaker assembly includes several dozen parts. in addition, the provision in existing circuit breaker assemblies of additional features and functions generally results in the inclusion of additional components for the performance of each additional function. Each of such components may include numerous additional parts, thus adding further to the complexity of the mechanism. One such added function is that of arc quenching which may be performed by any one of several types of arc quenching components, each requiring the inclusion in a circuit breaker of several additional parts. Likewise, the provision of trip-free operation, necessary in many commercial and military applications, may also necessitate the inclusion of several additional parts. Similarly, the provision of snap-action to insure that the circuit breaker contacts will open and close rapidly, independent of the operators skill, frequently requires the inclusion of an additional relatively intricate mechanism expressly for this purpose.

The present invention contemplates an advanced circuit breaker design having the inherent advantages of the electromechanical type circuit breakers and arranged to obviate the disadvantages generally characteristic of this type of circuit breaker. The present invention provides a circuit breaker assembly characterized by relatively few parts arranged to form an uncomplicated mechanism, the construction of which is generally symmetrical with respect to the entire assembly, each sub-assembly, and the individual parts thereof. This simplicity and symmetry ice of design greatly facilitates production, inspection, assembly, and operation of this device, in contrast to existing circuit breaker designs which are typically complicated and rely at many points on close manufacturing and operating tolerances. The present invention is enhanced by the fact that all of the parts are arranged to assume positive on or ott positions without the use of the locked or locking linkages generally included in known types of circuit breakers for this purpose. In addition, the symmetrical arrangement of parts Within the circuit breaker comprising the present invention renders this device shock and vibration proof with all of the parts continuously positioned under naturally balanced conditions, in contrast to the arrangements commonly provided in known types of circuit breakers wherein balanced conditions are insured by the addition of cumbersome counter weights, or complicated, mechanically awkward, linkages, if at all. Moreover, the construction of the instant invention is such that the imposition of an overload condition on the sensing means causes initial action at the most critical point within the circuit breaker assembly, namely, the electrical contacts, and therethrough transmits movement to the mechanism attached thereto which is of secondary importance to the electrical system in which the circuit breaker assembly is incorporated. This action is simultaneously effective to extinguish the arc on contact separation, using only the primary sensing means for this purpose. In contrast to this improved performance, existing circuit breakers are generally arranged so that the sensing means initiates movement of the mechanism at a point remote from the contacts, which movement must be transmitted through the mechanism before displacement of the contacts begins, resulting in inevitable delay in opening the contacts. Finally, the circuit breaker comprising the present invention offers a high degree of adaptability both as to its possible applications and as to its manner of operation. With regard to its applications it operates with equal effectiveness under all D. C. and A. C. circuit conditions and, insofar as A. C. circuits are concerned, regardless of the frequency or number of phases involved. With regard to its manner of operation, the illustrated embodiment discloses a push-pull actuator and a trip-free, automatically tripping, non-self-closing circuit breaker mechanism, but

it can readily be converted for use with a toggle-type actuator and into an all-manual, or self-closing circuit breaker mechanism by making very simple modifications.

An object of the present invention is the provision of a circuit breaker suitable for D. C. applications and all A. C. applications regardless of the frequencies or number of phases involved.

Another object is to provide a compact circuit breaker incorporating comparatively few parts arranged to form a relatively uncomplicated mechanism.

Still another object of this invention is to provide a circuit breaker of the quick-make, quick-break type characterized by positive action throughout its mechanism.

Yet another purpose is to provide a circuit breaker construction which is symmetrical and balanced so that it is inherently shock and vibration resistant.

A further purpose is the provision of a circuit breaker in which the element responsive to an overload condition acts first upon the circuit interrupting means.

A iinal purpose of this invention is to provide an arc extinguishing means which in integral with the sensing and contact separation means.

The exact nature of this invention as well as other objects and advantages thereof will be readily apparent from consideration of the following description in relation to the annexed drawing which shows a vertical section through a preferred embodiment of the present invention.

Referringnow to the drawing, wherein like reference characters designate like or corresponding parts, the circuit breaker supporting case generally designated by referencenumeral 12 may conveniently be formed by'avparr of matinghalves 13, only one of which is shown and bothof which are preferably made of suitable electricallyinsulating material. The portions 13 of the case maybe secured together by suitable through bolts, notshown, inserted through openings 14 to securely retain the. circuit breaker mechanism within the case 12. Only the actuator 16 and the wiring terminals 18 need extend through the otherwise fully enclosedcase 12 in order to be accessible from the outside. The case 12 can be secured'in any desired location, such as on a control panel,l by the insertion of. suitable attachment screws in thelinternally threaded inserts 24 fixedly secured withinandbetween theportions 13 of the case 12. Alternatively, the collar 26 shown formed integrally with the portions 13to encirclevthe actuator 16 may be replaced with. a metal collar 28shown in phantom lines which may be externally threaded for engagement with an internally threaded retainingl ring to form another meansI for mounting the'circuit breaker assembly. The variousV components of the circuit breaker mechanism within the case are all directly or indirectly supported by a mechanical frame fixedly secured within the case. However, in order to facilitate complete understanding of the significant features of the present invention there is no showing. of this mechanical frame in the drawing as a part separateV and distinct from the case 12. Instead, in the illustrative embodiment shown, this mechanical frame should be considered to be formed integrally with the case 12 although in practice it may be a separate part. In addition, it should be noted that several minor parts such as pins, stops, and return springs which would be desirable additions to this device have been omitted from the drawing to permit the clearest possible showing of the more significant features of this device. The stationary pin 30 is xedly secured to and projects from the interior surface of the case 12 to provide pivotal support forathe pair of opposed elongated members 32 engaging the circumferential surface of the pin as shown in the drawing. The members 32 are maintained in `floatingengagementwith said pin by a biasing means which may conveniently include a pair of Clshaped biasing springs 34, one .of which is shown broken away in the drawing to'reveala portion of the second one immediately behindv it, bothlconnected at their opposite ends with a pair of generally cylindrical rollers 36 by suitable connecting meanssuch as the pair of elongated shafts 54. The elongated members 32 as shown in the illustrative embodimentare preferably fabricated from a non-metallic substance, and each of these members is fitted with a slug 38 of magnetic material, which may be horse-shoeshaped and is preferably made of soft iron, fixedly secured to one side of theelongated member intermediate its ends. The respective slugs 38 are arranged so that their flats 40 adjoin each other in a closely spaced relationship when the contacts 44 are closed. The end of each elongated member 32 remote from the pivot 30 is fitted with an electrically insulating. base 42 upon which one o-f the pair of circuit breaker contacts 44 is mounted. l

The actuator mechanism includes the rollers 36 referred to above, eachV rotatably connected to a roller link 52 by means of one of the shafts 54 which also serves to connect the roller to the ends of the respective biasing springs 34. Therespective roller links are connected to opposite ends of the guide plate 576'by suitable means allowing limited play of the roller links 52 about the point of attachment. This means of attachment may consistof a pivotal connection or a hinged joint. The drawing shows one simple and convenient hinged arrangement which satisties the requirements of thismechanisrni In this illustrativeV embodiment, the respective 4: roller links 52 are loosely secured to the guide plate 56 for limited hinged movement relative thereto by the coacting restraining effect ofv shoulder 51, engaging the under surface of the guide plate 56, and an elongated up-A wardly extending portion 53 thereof, projecting through a suitable opening in guide platev 56 adjacent each end thereof and bent toward the actuator. 16 to lie adjacent the upper surface ofthe guide plate'56. In addition, the ends of the guide plate 56 are. provided with a pair of downwardly depending ears SSfarranged to restrictthe angular movement o-f the roller links 52 relative tothe guide plate S6, whereby the ears 58 in cooperation with the outwardly sloping roller engaging cam surfaces or faces 46 on the members..32'. provide a positive means for separating the contacts44 in the event that they become welded together. A centrally disposed hole 60 through the guide plate 56 is provided to receive the reduced stem portion 62 of the push-pull actuator 16. With this arrangement, restricted movementv of the actuator 16 relative to thetguideV plate 56 is permitted within the limits established. by the shoulder 64 on the actuator 16 adjacent its stem portion 62 Wand the retaining ring 66 which is tted into an annular groove 68 adjacent the other end of the stem portion 62. The actuator return spring72 is provided to assure the return of the actuator to the olf position notwithstanding its limited sliding movement relative to the guide plate 56.

The automatic actuating means for this ycircuit breaker includes a coil winding 82 which may conveniently be wound upon a coil bobbin 84 and be located within the case 12 by a coil positioner 86 and brackets 88 or other suitable supporting'means to maintain the winding 82 in its proper position encircling the elongated members 32 and the slugs 38 attached thereto. The winding 82 is connected as sho-wn'in the drawing in series withk the contacts 44between the-wiring terminals 18` by means of the leads 90, 91 and 92. With this arrangement the coil winding 82 operates in the manner described below to separate the contacts i4-when trouble develops in the circuit in which this device is incorporated, and simultaneously functions as an arcquenchingmeans. As a further protection against the'adverse effects of arcing, the circuit breaker comprising the present invention may be provided with arc` protectors 94 vmounted as shown in the drawing adjacent the. ends of the respective slugs 38 nearest the contacts 44.

The variousphases of operation of the present inventionwill now be described in sequence beginning with manual movement from the on position illustrated in the accompanying drawing to the off position. This manual movement is' brought about by pulling the actuator 16 outwardly from the case 12. until the collar 64 on the actuator 16 strikes a suitable stop such as the boss 96 on the interior surface of the case 12, so that the retaining ring 66 secured to the stem 62 of the actuator 16 is brought into engagement with thev under side of the guide plate` 56 and. moves it away from the pivot 30. This movement `of the guide plate 56 istransmitted throiigh the roller links 52 and the shafts 54v to therespectiveV rollers 36 to displace these rollers from one side of the stationary pivot 30 to the other along the respective faces 46 on the outer sides ofthe elongated members 32. These faces 46 are sloped slightly away from eachother toward the upper ends of the respective members 32 when the contacts 44v are engaged as shown in the drawing so that in the on position of the mechanism illustrated the rollers are maintained in engagement with the shoulders 47 on thelmembers 32 with their points of contact with the faces 46 below -the axis of the pivot 30. The-rollers and the mechanism connected thereto are` stabilized in this position by the continuous clamping action of the biasing springs 34, until this clamping action of the springs 34 is overpowered by the positive manual displacement of thev actuator 16 transmitted through the actuator mech.- anism described above. As the rollers 36 pass to the other side of the stationary pivot in response to outward displacement of the actuator 16, the clamping action of the biasing springs 34 imposed upon the rollers through the shafts 54 as the rollers 36 are moved along the oppositely sloped faces 46 causes the elongated members 32 to rotate about the pivot 30 in opposite directions to separate the contacts 44. When the sloped ends 48 of the members 32 come into engagement, the direction of slope of the faces 46 has been reversed by opposite angular displacement of respective members 32 so that the clamping action of the biasing springs 34 applied to the members 32 through shafts 54 and rollers 36 maintains the actuator mechanism in the off position with the collar 64 in engagement with the boss 96 to deenergize a circuit in which this device is included. The relationship between the roller links 52 and the ears 58 depending from the guide plate 56 noted above restricts the lateral displacement of the rollers 36 during their movement along the sloped faces 46. With this arrangement, failure of the members 32 to rotate about the pivot 30 due to welded contacts 44 forces the rollers 36 and the roller links 52 outwardly as the rollers are moved along the oppositely sloped faces 46 until the links 52 engage the ears 58. Thereafter, further travel of the rollers along the sloped faces 46 breaks apart the welded contacts. rThis assured separation of the contacts by operation of the actuator mechanism is positive action of the type essential to reliable circuit breakers.

The return movement of the circuit breaker from the off to the on position is achieved manually by pushing the actuator 16 inwardly relative to the case 12 until the collar 64 on the actuator engages the adjacent surface of the guide plate 56 and thus moves the guide plate toward the pivot 30. This movement of the guide plate S6 is transmitted through the roller links 52 and the shafts 54 to the rollers 36 to return them to the opposite side of the stationary pivot Si? so that the clamping action of the springs 34 upon the oppositely sloped faces 46 becomes effective to rotate the respective elongated members 32 in opposite directions until the contacts 44 are once more brought into engagement with each other in the position shown in the drawing. The rotation of the iembers 32 is accompanied by a reversal of the slope of faces 46 so that the clamping action of the springs 34 moves the rollers 36 once more into engagement with the respective shoulders 47.

The foregoing descriptions cover the manual phases of operation of the present invention by manipulation of the mechanical components thereof. It will be noted, in this connection, that the continuous clamping action of the retaining springs 34 in cooperation with the floating relationship of the members 32 to the stationary pivot 3i) produces a snap-action both during opening and closing movements of the mechanism, a feature highly desirable in circuit breaker assemblies since it offsets any possible lack of skill on the part of the operator.

The third phase of operation involves automatic movement of the circuit breaker from the on to the off position in response to an overload condition. It will be noted from the description above that when the circuit breaker co-mprising the present invention is connected by means of the wiring terminals 1S between a line and a load, the winding 52 is energized Whenever the contacts 44 are in engagement with each other. Energization of the coil 82 estabiishes magnetic lines of force through the center of the coil and hence about the slugs 38. In the presence of this field, the two slugs 38 assume like magnetic polarities with respect to each other by virtue of magnetic induction. For example, the two slug faces 40 nearest the contacts 44 may become magnetic north poles while the two opposite faces nearest the pivot 30 may become magnetic south poles. In accordance with the basic concepts of electromagnetism, these like magnetic poles repel each other. However, as long as the energizing current passing through the winding 82 is comparatively low, as it is under normal operating conditions, the force exerted by the biasing springs 34 upon the elongated members 32 will not allow movement of the these members away from each other in response to the repelling force exerted by the respective slugs. Whenever an overload condition arises, the current ow through the coil winding 82 will be substantially increased with a corresponding increase in the magnetic field through the center of the coil resulting in increased flux density within the slugs 33 which is accompanied by an increase in the repelling force generated between the respective slugs sufficient to overcome the restraint imposed by the biasing springs 34. When such a condition arises, the elongated members 32 and the contacts 44 attached thereto will be forced apart immediately to interrupt the circuit. As the members 32 are forced apart by the repelling force between the slugs 38, the opposed slopes of the respective faces 46 upon which the rollers move will be reversed so that the rollers are compelled to travel along the faces 46 to the other side of the stationary pivot 30. This movement of the rollers and the links 52 to which they are connected displaces the guide plate 56 and the return spring 72 which moves the actuator 16 to its off position and the clamping action of the springs 34 upon the reversed slopes of the faces 46 maintains the entire actuating mechanism in the off position until the circuit breaker is manually reset. The continuously imposed clamping action of the biasing springs 34 is also effective during this phase of the operation to produce what is known as snap action and thereby insure very rapid separation of the contacts 44. Moreover, the actuator mechanism of the present invention is so arranged that automatic contact opening in response to abnormal conditions will take place even while the actuator is being depressed manually, either accidentally or intentionally, whereby this circuit breaker is rendered trip-free. This trip-free feature is provided by the spacing of the collar 64 and the ring 66 along the stem portion 62 of the actuator 16 to provide limited sliding action between the actuator 16 and the guide plate 56, and by the selection of suitable contours for the faces 46 on the elongated members 32 along which the rollers 36 travel.

The circuit breaker shown in the accompanying drawing is reset after automatic movement to the off position by manual operation of the actuator 1 6 in exactly the saine fashion as that described above.

It will be noted that the design of the present invention is such that it is suitable for use not only in nonpolarized D. C. circuit connections or reversed D. C. current applications but aiso for A. C. current installations regardless of the A. C. frequency involved. This wide adaptability is made possible by the fact that the slugs 38, preferably made from soft iron, reverse their magnetic polarity as the direction of the coil field reverses. Moreover, since little or no iron is used within the magnetic circuit including the coil itself, this device may be used with A. C. frequencies of 400 cycles per second, for example, frequently employed in modern aircraft electrical systems. In addition, the design of the instant invention includes inherent arc quenching based upon the well known blow-out magnet principle without the incorporation of any additional components expressly for this purpose. The are which forms as the contacts 44 are separated will momentarily maintain the electric circuit and with it the energization of the coil 82 to maintain the magnetic field generated by the energized coil. Thus, the arc is exposed to the effects of the coil field and the electromotive force induced in the arc will cause its displacement and subsequent interruption in a shorter time interval. Furthermore, it should be noted that, once the internal wiring of the circuit breaker is connected, the arc will be blown in the same direction, regardless of the external circuit connection, hence, uncomplicated auxiliary means may readily be provided to direct the arc intothepreferre'dlzonesat all times. A' further advantage inherent in the design ofthe; circuit breakerdescribed above. is'Y that theforce.A applied; to f induce:` contact a separation and the'blowi out action increaseY as the portion of the: coil. energizing current due, toV overload increases. Consequently, Vb'othiricr'eased opening. force` and blowout action become availableas the severity of the undesirable condition rwithin the circuit increasesin magnitude.

Several alternate methods of. construction avail themselves on the basisnof.y the foregoing description. The push-pull type circuit breaker actuator 16 shown in the drawing-can readilyV be` replaced-by a toggle type actuator arranged to actupon the Vguide plate 56 in a manner well known; in the circuit breaker' art: The single break arrangement shown in the drawing can be replaced by a triple. break arrangement by modificationY of the elongated members 32 particularly in regard to their current-carrying portions, andfbyireplacingQthe flexible wireleads 91 and 92 with mating contacts mounted upon the tails of the movable elongatedmembers-32 and upon the case 12 for connection' throughthe Vcoil 82 tothe rigid electrical conducting portions to which the wiring terminals 18 are integrally connectedas shownin the drawing. Moreover, the turns of thecoil 32 may be tapped; at various points and the respective leadsV may be brought out to additional circuit breaker terminals to provide additional connections for specific controljand power circuits. Finally, the single pole circuit breaker unit illustrated in the drawing and described herein can readily be modified to operate in conjunction with one or more additional similar units to constitute a multi-pole circuit breaker assembly.

Thus, the present invention provides a unique circuit breaker which initiates rautomatic operation in response to an overload condition at the most critical points of a circuit making and breaking device, namely, at the contacts,y and simultaneously employs the action initiating means for arc extinction. With the parts movement transmitted fromthe contacts through the actuator mechanism to the actuator the usual direction of such movement is reversed and hence any time lags which would ordinarily delay separation of contacts occur in this device after such separation has been completed.y Thiscircuit breaker also provides symmetrically shaped and arranged mechanical elements inlwhich the masses are balanced and includes oating contacts and contact supporting members. With such an arrangement of the mechanical elements, the present invention is highly resistant to both shock and vibration, and, therefore, is well suited for use under extremely adverse operating conditions such as those characterizing aircraft installations.

Obviously, many modifications and variations of the present invention are possible in the light of the above teachings. It is, therefore, to be understood that within the scope of the appended claims the invention may be practiced otherwise than as specifically described.

What is claimed is:

l. A circuit breaker comprising a pair of movably mounted electrical contact assemblies, including a pair of electrical contacts movable between a first position in mutual engagement and a second position out of engagement, manually operable mechanical means for selectively maintaining said contacts in engagement and out of engagement, a pair of opposed slugs of magnetic material` attached to they respective contact assemblies and disposed immediately adjacent each other when said contacts are in engagement, an electromagnetic overload sensing means for generating a magnetic field proportional to the flow of current therethrough, said electromagnetic means being disposed so that the magnetic field generated thereby envelopes said slugs and induces therein a force tending to separate said slugs and the contact assemblies to which -they are attached, and electrical conduit means for connecting said electrical contacts and said electromagnetic means in series, whereby an overload condition in the circuit incluriling the contacts and saidelectromagnetic means produces an increase in the force` tending, to separate said slugs sufficient to overcome said mechanical'means to; move saidlr-kcontacts from their iirstposition in` mutual engagement to theirsecondposia tion out of'erigagement inwhich they are retained by said.

mechanical means.`

2. A circuit breaker assembly` including a pair of mov-V able electrical contacts, a pair of electrical contact supporting. members to which said contacts are secured mounted for movement-between a first extreme position in which said contacts are in engagement and a secondL extreme position in whichl said contacts are out of enr-- gagement, a pair of-opposed flux responsive means at-y tached to the respective contact supporting members to= sense the presence o f a magnetic field and arranged sol that they are immediately adjacent each other when said` members are in their rst extreme position, electromagnetic means arranged to generate a magnetic field proportional to the current ow therethrough enveloping said.

in said second extreme position, whereby a critical increase in the current How through the electromagnetic means `and in the magnetic field induced thereby causes said flux responsive means to repel each other with a force suiiicient to overpower said biasing means and move saidmembers to their second extreme position from their first extreme position.

3. An electromagnetic circuit breaker comprising a centrally disposed pivot pin, a pair of identical elongated members disposed in opposed positions on opposite sides of said pivot pin, a spring biasing means in engagement with both said elongated members adjacent one end thereof and arranged to apply opposed forces to the elongated members to maintain the respective elongated members in pivotal bearing relationship with opposite sides of said pivot pin, said biasing means being movable along said members to positions on opposite sides of said pivot pin, a pair of electrical contactsvmounted in opposed relation on the other end of the respective elongated members and arranged so that they are placed in mutual engagement when the elongated members are rotated toward each other about said pivot pin by movement of said biasing means past said pivot pin, a pair of soft iron slugs mounted in opposed positions intermediate the ends oi' the respective elongated members, and an electromagnetic coil encircling the slugs and the portions of thc elongated members on which they are mounted, whereby an overload imposed upon said coil creates a magnetic field effective to induce like magnetic polarities in said slugs of suicient magnitude to cause said slugs to repel each other to force the electrical contacts out of engagement and thereby move said biasing means past said pivot pin.

4. A device as described in claim 3, in which said spring biasing means is C-shaped with the free ends biased toward each other, and in which the opposed forces exerted by the biasing means upon said elongated members is applied through a pair of rollers, each in engagement with a substantially iiatcam surface on the edge of one said elongated member, each cam surface including portions extending in opposite directions from a point adjacent said pivot pin, the respective cam surfaces being angularly displaced to reverse their effective slopes by movement of said rollers from a position on one side of said pivot pin to a position on the other side of said pivot pin, whereby said electrical contacts are biased toward each. other by said. biasing means when the respective rollers are in engagement with one portion of the respectivecam surfaces andthe electrical contacts are. biased away from each other when the respective rollers are in engagement with the other portion of the respective cam surfaces.

5. A circuit breaker assembly comprising a manually operable actuator, a pair of movably mounted electrical contact supporting members, a pair of electrical contacts mounted upon the respective contact supporting members, an actuator mechanism operatively inter-connecting said actuator and said contact supporting members and arranged so that suitable movement of said actuator moves said electrical contacts into and out of mutual engagement, said actuator mechanism including means for selectively maintaining said Contact supporting members in either of two extreme positions, a pair of slugs of magnetic material attached to the respective contact supporting members adjacent the respective electrical contacts, and a substantially annular electromagnetic coil disposed so that it encircles said contact supporting members and the slugs attached thereto, whereby excessive Icurrent in said coil will generate a field effective to cause said slugs to repel each other with a force sufficient to move said contact supporting members to their other eXtreme position.

6. A circuit breaker assembly comprising a manually operable actuator, a matched pair of opposed rotatably mounted electrical contact supporting members, a pair of movable electrical contacts fixedly secured to the respective contact supporting members, a mechanical actuator mechanism operatively interconnecting said actuator and said contact supporting members and arranged so that suitable movement of said actuator moves said electrical contacts into and out of mutual engagement, said actuator mechanism including a double acting biasing means selectively effective to maintain said Contact supporting members in one of two extreme positions, a matched pair of opposed slugs of magnetic material attached to the respective contact supporting members and disposed so that they are closely adjacent each other when said electrical contacts are in engagement, and a generally annular electromagnetic coil fixedly secured in a position in which is encircles said contact supporting members and the slugs attached thereto, said electromagnet being connected in series with said contacts within an electrical circuit, whereby an overload condition in said circuit is effective to generate a reaction between said slugs sufficient to overcome said biasing means and thereby effect separation of said electrical contacts.

7. A circuit breaker assembly comprising a supporting case, a manually operable actuator reciprocably mounted upon said case, a fixed pivot secured centrally of said case, a matched pair of opposed electrical contact supporting members rotatably mounted upon opposite sides of said fixed pivot, a pair of movable electrical contacts fixedly secured to corresponding ends of the respective supporting members, an actuator mechanism comprising a mechanical linkage operatively interconnecting said actuator and said contact supporting members and including a biasing means disposed in continuous clamping engagement with the respective contact supporting members, said actuator mechanism being arranged to move said biasing means back and forth along said members and past said fixed pivot to engage the contacts in response to movement of the actuator in one direction and to disengage the contacts in response to movement of the actuator in the other direction, a matched pair of opposed slugs of magnetic material attached to the respective contact supporting members and disposed so that they are closely adjacent each other when said contacts are in engagement, and an annular electromagnet Xedly secured in a position in which it encircles said contact supporting members and the slugs attached thereto, said electromagnet being connected in series with said contacts within an electrical circuit, whereby said electromagnet forms an overload sensing means operable to disengage said contacts immediately in response to an overload condition by generating a repelling force between said slugs sufficient to overpower said biasing means.

8. A circuit breaker assembly comprising a manually operable actuator, a matched pair of opposed rotatably mounted electrical contact supporting members, a pair of movable electrical contacts fixedly secured to the respective contact supporting members, a mechanical actuator mechanism operatively interconnecting said actuator and said contact supporting members and arranged so that suitable movement of said actuator moves said electrical contacts into and out of mutual engagement, said actuator mechanism including means for maintaining said contact supporting members in either of two extreme positions, a matched pair of opposed slugs of magnetic material attached to the respective contact supporting members and disposed so that they are closely adjacent each other when said electrical contacts are in engagement, and an annular electromagnetic coil xedly secured in a position in which it encircles said contact supporting members and the respective slugs attached thereto, said contacts being disposed within the immediate influence of said coil, whereby the magnetic field generated by said coil effects arc quench ing upon separation of said contacts.

References Cited in the tile of this patent UNITED STATES PATENTS 443,693 Wood Dec. 30, 1890 1,185,851 Snyder June 6, 1916 1,643,415 Moore Sept. 27, 1927 2,286,800 Gustin June 16, 1942 2,326,232 Krieger Aug. 10, 1943 2,644,869 Sevison July 7, 1953 FOREIGN PATENTS 252,185 Great Britain Dec. 9, 1926 294,682 Great Britain July 30, 1928 536,695 Great Britain May 23, 1941 519,462 Germany Feb. 28, 1931` 

